The Short Answer
When an air conditioner runs but doesn't cool an Ottawa home, the usual causes are a dirty air filter, a frozen evaporator coil, a dirty outdoor condenser, a thermostat problem, or low refrigerant from a leak. Start by replacing the filter, clearing the outdoor unit, and checking the thermostat. If it still won't cool — especially if there's ice on the lines — call Dtech at (343) 227-3610.
On a hot, humid Ottawa afternoon, an air conditioner that runs but doesn't actually cool is a real problem. Before you call for service, there are several things you can check — and some you can fix yourself. Here are the most common reasons an AC stops cooling, roughly from easiest to most technical.
1. A Dirty Air Filter
The most common cause is also the easiest to fix. A clogged filter starves the system of airflow, which cripples cooling and can even freeze the indoor coil. Check your filter — if it's dirty, replace it. During Ottawa's cooling season, change it every 1–3 months.
2. A Frozen Evaporator Coil
If you see ice on the refrigerant lines or the indoor coil, the system has frozen — usually from restricted airflow or low refrigerant. Turn the AC off (set the fan to "ON" to help it thaw), replace the filter, and give it a few hours. If it refreezes after restarting, you have an airflow or refrigerant issue that needs a technician.
3. A Dirty or Blocked Outdoor Condenser
The outdoor unit sheds your home's heat, and it can't do that if it's clogged with grass clippings, leaves, cottonwood fluff or dirt. Gently clear debris and vegetation at least 60 cm around the unit, and rinse the fins with a hose on low pressure. A smothered condenser is a very common Ottawa summer problem.
4. A Thermostat Problem
Confirm the thermostat is set to "COOL," the temperature is below the room reading, and the batteries are fresh. A failing thermostat or wiring issue can stop the system from cooling even when everything else works.
5. Low Refrigerant (a Leak)
Refrigerant isn't consumed — if it's low, there's a leak. Low refrigerant reduces cooling and often freezes the coil. This needs a licensed technician to locate and repair the leak and recharge the system; simply topping it up is a temporary fix that wastes money.
6. Compressor or Capacitor Issues
The compressor is the heart of the system. A failed run capacitor or a struggling compressor can leave the fan spinning while little or no cooling happens. These are repairs for a professional, and on an older unit, they're often the point where replacement makes more sense.
7. An Aging or Undersized System
If your air conditioner is 10–15+ years old, uses phased-out R-22 refrigerant, or was never sized correctly for your home, it may simply be at the end of its useful life. In that case, a new high-efficiency unit — or a heat pump that also heats — is the better investment.
How to Prevent AC Problems in Ottawa
A little upkeep prevents most mid-summer breakdowns. Change your filter every one to three months, keep the outdoor condenser clear of grass, leaves and cottonwood fluff, and make sure shrubs and fences leave at least 60 cm of breathing room around the unit. Keep supply and return vents open and unobstructed so airflow stays strong, and rinse the outdoor coil gently with a hose at the start of each cooling season. Most importantly, book an annual AC tune-up in spring: a technician checks the refrigerant charge, cleans the coils, tests the capacitor and compressor, and clears the condensate drain before the first heat wave — catching small issues before they leave you without cooling on a 32°C Ottawa afternoon. A spring tune-up also keeps your system running at its rated efficiency, which shows up on your summer hydro bill.
When to Call Dtech
If the filter, outdoor unit and thermostat checks don't restore cooling — or you see ice on the lines — it's time for a technician. Dtech provides fast AC repair across Ottawa with upfront pricing and honest repair-or-replace advice. Call (343) 227-3610 or book service online and we'll get your home comfortable again.
Frequently Asked Questions
Why is my AC running but not cooling?
The most common causes are a clogged air filter restricting airflow, a frozen evaporator coil, a dirty outdoor condenser, a thermostat set wrong, or low refrigerant from a leak. Start with the filter and the outdoor unit — if those are clear and it still won't cool, you likely need a technician.
Should I turn off my AC if it's not cooling?
If you see ice on the refrigerant lines or indoor coil, yes — turn it off and let it thaw, since running a frozen system can damage the compressor. For other issues, you can leave it off until you've checked the filter and thermostat. If simple checks don't help, call for service.
Why is my AC freezing up in summer?
A frozen coil usually comes from restricted airflow (dirty filter or blocked vents) or low refrigerant. The coil gets too cold and condensation freezes on it. Turn the system off to thaw, replace the filter, and if it refreezes, you likely have a refrigerant or airflow problem that needs a technician.
How much does AC repair cost in Ottawa?
Most AC repairs in Ottawa run $150–$600 depending on the part and labour. A refrigerant leak repair or compressor issue costs more. Dtech provides upfront pricing before any work, and if an aging unit isn't worth repairing, we'll tell you and outline replacement options.
Could low refrigerant be why my AC isn't cooling?
Yes. Low refrigerant — almost always from a leak, since it isn't consumed — reduces cooling capacity and can freeze the coil. Simply "topping up" without fixing the leak is a temporary band-aid. A technician should find and repair the leak, then recharge the system correctly.
